Composition for use in a water reservoir

ABSTRACT

Composition for use in a water tank in the kitchen or sanitary sector, characterized by a basic composition essentially evolving its function following addition to a first water filling of the water tank, in the form of a tablet and at least one particle, with at least one core, which comprises at least one substance evolving its function essentially following an at least partial emptying of the first water filling from the water tank and the inflow of fresh water and a covering substantially completely surrounding the core or cores comprising at least one compound, whose solubility increases with decreasing concentration of a specific ion in the surrounding medium, the at least one particle being so arranged in or on the tablet that the surface of the particle or particles is at most only partly in direct contact with the surface of the basic composition surrounding the same and the concentration of the specific ion in the local environment of the particle or particles is sufficiently high up to a substantially complete dissolving of the tablet in order to prevent a substantial dissolving of the covering or a substantial detachment of the covering from the core or cores.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Section 371 of International Application No.PCT/EP98/05263, filed Jul. 23, 1999, the disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a composition for use in a water tankin the kitchen or sanitary sector.

Such compositions are known in numerous different forms for differentapplications, e.g. for deliming coffee machines or for cleaning anddeliming toilets as an additive to cisterns.

The aim of the invention was to permit the simultaneous charging ofsubstances possibly not completely compatible when used simultaneouslyand which evolve their functions at different, defined times.

DE-OS 20 65 153 and DE-OS 20 07 413 disclose detergent pellets for useas washing agents, in which it is inter alia provided to combine twocomponents with different functionalities. The structure is formed froma covering or enveloping shell, which is e.g. formed from two shellhalves, which comprise a cleaning agent, and a cavity surrounded by theshells and which contains additives such as softeners, brighteners, etc.

British patent 1 390 503 discloses a liquid cleaning agent or detergentwhich contains capsules, which are insoluble in the composition, butrelease their content when the composition is diluted with water. Thisobjective is achieved in that the capsules are coated with a substance,which has a poor solubility in water solutions with a high ionicstrength, but which is soluble if the ionic strength is reduced bydilution. It is pointed out that this procedure can be used in order toincorporate materials into the liquid cleaning agent, which in thelatter are unstable or would produce an instability if added directly.It is also proposed to use this procedure for delaying the release of aspecific substance.

U.S. Pat. No. 4,082,678 describes a fabric conditioner, which comprisesa closed container containing a releasable agent and which is used formaking water-insoluble or non-dispersible an inner container located inthe first container and which is normally water-soluble orwater-dispersible, the inner container containing a fabric conditioner.

Japanese patent applications KOKAI 60-141705, 61-28440, 61-28441,61-28596, 61-28597 and 61-28598 describe processes for the production ofpH-sensitive microcapsules for use in detergents. The pH-sensitivecoating is a copolymer of the following monomers:

A) at least one basic monomer of formula I:

in which R is hydrogen or a methyl group and R¹ and R² in each case analkyl group with 1 to 3 carbon atoms and x is an integer from 1 to 4,

B) at least one monomer which is insoluble or difficultly soluble inwater and

C) at least one water-soluble monomer.

It is pointed out that the described polymers are insoluble at apH-value of 9.5 or higher and are soluble at a pH-value of 8.5 or lower.Different ingredients of cleaning agent compositions are described,which can be successfully and usefully coated with the describedpolymers. The aim of the invention described therein is to protectsubstances, which only evolve their function during the rinsing processup to the start of the latter and then to release them as immediately aspossible. A disadvantage of the solution described in these Japanesepatent applications is that the enveloped particles are in directcontact with non-alkaline washing water at the start of the washingcycle, which can give rise to a partial dissolving of the protectivecovering.

Japanese patent KOKAI 50-77406 discloses a washing aid, which issurrounded by a water-soluble covering or envelope, obtained by mixingpolyvinyl acetal dialkyl aminoacetate and at least one organic acid,which is solid at room temperature. This protective envelope is intendedto protect the washing aid during the main washing cycle and to releaseit during rinsing cycles. The described compound reacts to the pH-valuechange between the main washing cycle and the rinsing cycle. Here againthe disadvantage exists of a possible partial dissolving of theprotective envelope at the start of the washing cycle.

European patent applications EP 284 191 A2 and EP 284 334 A2 disclose awater-soluble polymer film for releasing washing additives during therinsing cycle of washing machines, remaining intact during the normalwashing cycle over a range of typical temperatures and rapidlydissolving during the rinsing cycle. These applications point out thatthe use of pH-sensitive coatings was admittedly known, but that thesefilms are normally also temperature-sensitive, so that they do notremain reliably stable during the different temperatures of the washingcycle. The solution proposed is a pH-dependent material (whichundesirably also has a positive, temperature-dependent dissolvingbehaviour) which is combined with a material having a negative,temperature-dependent dissolving behaviour. This combination is supposedto guarantee that the coatings do not dissolve at the high temperaturesat the start of the washing cycle (in particular the very hightemperatures occurring in American machines).

European patent application EP 481 547 A1 discloses multilayerdishwashing machine tablets having a core, a separating layersurrounding the core and an outer layer for the sequential release ofthe ingredients of the different layers. This tablet is fundamentallyintended to solve two problems, namely 1) incompatible materials can beformulated together in a single tablet and released at different timesin order to avoid mutual influencing and 2) compositions, which areintended to evolve their functions at different times, can be formulatedin a single tablet.

One of the disadvantages of the prior art described in this document isthat the only production process described is the successive moulding ofthe individual components. This gives rise to the risk that the core orcore envelope is deformed, which can firstly lead to damage (andtherefore a reduction of the protective action) to the core envelope andsecondly (as a function of the core composition) can give rise a“bleeding” of the core into the material of the envelope and the basiccomposition. In addition, the intimate full-surface contact between theindividual layers can lead to reactions occurring in the boundary layerswhich are undesired, particularly between the envelope and the outerlayer.

The second important disadvantage of this prior art is that forinitiating the dissolving of the enveloping layer the temperature and inparticular the contact time with the washing solution is used as thetriggering factor, which consequently clearly limits the practicalusability of the products described.

PCT application WO 95/29982 discloses a dishwashing machine rinsingagent with a delayed release of a clear rinsing agent in the form of anonionic surfactant, which together with an inorganic builder salt formsa core particle, which is provided with a wax-like covering in order toensure the delayed release. This covering is a substance which does notmelt at the operating temperatures encountered during the cleaningcycle, but which at alkaline pH-values is so gradually chemicallydisintegrated that there is still an effective clear rinsing agentquantity present at the end of the main cleaning cycle and istransferred into the rinse clear cycle.

It is disadvantageous that the covering is rendered soluble by chemicalsaponification at alkaline pH-values, so that the time at which theclear rinsing substance is released from the core is a function both ofthe temperature and the length of the main cleaning cycle. The patentapplication contains no teaching as to how a product is to be formulatedwith which the clear rinsing agent can be released in all washingprograms of any machine type only during the rinse clear cycle. Finallythe product is a mixture of granular cleaning agents and granular clearrinsing particles.

In view of the prior art described, the problem of the present inventionis to provide a composition making it possible to release at different,defined times simultaneously charged products with differentfunctionalities. The aim is to achieve this without significantrestriction to the choice of the materials to be combined together.

SUMMARY OF THE INVENTION

According to the invention this problem is solved by a compositioncharacterized by a basic composition evolving its function essentiallyfollowing addition to a first water filling of the water tank, in theform of a tablet, and at least one particle with at least one corecomprising at least one substance, which evolves its functionsubstantially after an at least partial emptying of the first waterfilling from the water tank and the inflow of fresh water thereto, and acovering substantially completely surround the core or cores andcomprising at least one compound, whose solubility increases withdecreasing concentration of a specific ion in the surrounding medium,the at least one particle being so arranged in or on the tablet that thesurface of the particle or particles at the most is in partial directcontact with the surface of the basic composition surrounding the same,and the concentration of the specific ion in the local environment ofthe particle or particles is sufficiently high up to a substantiallycomplete dissolving of the tablet to prevent a significant dissolving ofthe covering or a significant detachment of the covering from the coreor cores.

Preferably the or all the particles are received in at least one tabletcavity completely surrounded by the basic composition and having alarger volume than the or all the particles received in the particularcavity.

In an alternative, the particle or particles can be loosely arranged inthe interior of the cavity.

In a particularly preferred embodiment of the invention the particle orparticles are fixed in the interior of the cavity.

According to the invention the particle or particles are fixed in theinterior of the cavity by an adhesive.

In an alternative embodiment of the invention the cavity is placedsubstantially centrally in the tablet interior.

The tablet has a single, substantially spherical cavity.

According to the invention the cavity receives a single, substantiallyspherical particle, whose external diameter is smaller than the internaldiameter of the cavity.

According to an alternative embodiment of the invention the or all theparticles are received in at least one cavity of the tablet, which isonly partly surrounded by the basic composition.

The cavity is preferably a depression in one of the surfaces of thetablet, in which the particle or particles are at least partiallyreceived.

The particle or particles are so received in the cavity or depressionthat it or they do not project over the surface or surfaces of thetablet.

According to an embodiment of the invention the cavity or depression hasa substantially circular cross-sectional face parallel to one of thesurfaces to which it opens or in which it is located.

According to a particular embodiment of the invention the cavity ordepression only opens to such an extent to the surface or surfaces thatthe particles received therein cannot pass through the opening oropenings of the cavity or depression.

Preferably the particle or particles are loosely arranged in the cavityor depression.

It is also possible for the particle or particles to be fixed in thecavity or depression, said fixing preferably taking place with anadhesive.

In preferred manner according to the invention the covering comprises atleast one compound, which is not or is only slightly soluble at theconcentration of the specific ion prior to the inflow of fresh water andat the concentration of the specific ion following the inflow of anadequate fresh water quantity has such an adequate solubility that it isso substantially dissolved or detached from the core or cores that an atleast partial escape of the core material into the surrounding medium ispossible.

Preferably the solubility of the compound increases with decreasing OH⁻ionic concentration and therefore decreasing pH-value in the surroundingmedium.

Preferably the compound comprises a polymer, in particularly preferredmanner a pH-sensitive polymer, which comprises at least one repeat unit,which has at least one basic function, which is not part of the polymerbackbone chain.

In a preferred embodiment the polymer comprises at least one repeatunit, which is based on a compound selected from the group comprisingvinyl alcohol derivatives, acrylates or alkyl acrylates having saidbasic function.

According to a special embodiment of the invention the polymer is acarbohydrate functionalized with said basic function.

The aforementioned basic function is preferably an amine, inparticularly preferred manner a secondary or tertiary amine.

According to an alternative, the repeat unit is based on a compoundhaving the following formula III:

in which G is a linking group selected from —COO—, —OCO—, —CONH—,—NHCO—, —NHCONH—, —NHCOO—, —OCONH—, or —OCOO—, each R₁ independently ofone another is hydrogen or an alkyl group with 1 to 3 carbon atoms, eachR₂ independently of one another is hydrogen or an alkyl group with 1 to5 carbon atoms, and x is an integer from 1 to 6.

Preferably the repeat unit is based on a compound with the followingformula IV:

in which R₁ independently of one another is hydrogen or an alkyl groupwith 1 to 3 carbon atoms, R₂ independently of one another hydrogen or analkyl group with 1 to 5 carbon atoms and x is an integer from 1 to 6.

According to another embodiment of the invention the basic function isan imine or a basic, aromatic N-containing group, preferably a pyridinegroup or an imidazole group.

According to a further embodiment the pH-sensitive polymer is a polymerderived from chitosan.

The invention finally proposes that the compound comprisesK-carrageenan.

According to the invention the solubility of the compound increases withdecreasing H⁺ ionic concentration and therefore increasing pH-value inthe surrounding medium.

The compound preferably comprises a polymer.

According to an embodiment of the invention the compound comprises apH-value-sensitive polymer, which comprises at least one repeat unit,which is based on a compound comprising an acid function.

According to an alternative the polymer comprises at least one repeatunit, which is based on a compound selected from the group comprisingvinyl alcohol derivatives, acrylates or alkyl acrylates comprising saidacid function.

The polymer is preferably a carbohydrate functionalized with said acidfunction.

In particularly preferred manner the acid function is a carboxyl group.

According to an alternative the repeat unit is based on a compound withthe following formula V:

in which G is a link group selected from —COO—, —OCO—, —CONH—, —NHCO—,—NHCONH—, —NHCOO—, —OCONH— or —OCOO—, B independently of one another ahydrocarbon group selected from straight or branched, saturated orunsaturated, optionally substituted alkylene, arylene or aralkylene, Akis hydrogen or an alkyl group, preferably with 1 to 4 carbon atoms, x, yand z independently of one another are either 0 or 1 and w is an integerfrom 1 to 3.

The repeat unit is preferably based on a compound with the followingformula VI:

in which B independently of one another is a hydrocarbon group selectedfrom straight or branched, saturated or unsaturated, optionallysubstituted alkylene, arylene or aralkylene, Ak is hydrogen or an alkylgroup, preferably with 1 to 4 carbon atoms, y and z independently of oneanother are either 0 or 1 and w is an integer from 1 to 3.

Preferably the pH-sensitive polymer is derived from a polysaccharide bypartial esterification of some of its free hydroxyl groups with apolycarboxylic acid and/or by partial etherification of some of its freehydroxyl groups with a product obtained by esterifying one mole of apolycarboxylic acid with 1 mole of a polyol.

According to the invention the core or cores comprise at least onematerial selected from the group consisting of fragrances, disinfectantsand pH-indicators.

According to an embodiment of the invention the core or at least part ofthe cores is in the form of an encapsulated liquid.

In particularly preferred manner the core or at least a part of thecores is in a solid form.

The composition according to the invention is characterized in that itsolves the set problem with excellent results. The basic composition inthe form of a tablet is dissolved following addition to the waterfilling of the water tank and can evolve its corresponding, intendedaction (cleaning, deliming, etc.). The particle located in or on thetablet contains as the core material that substance or substancesevolving their main function only after an at least partial emptying ofthe water tank and the inflow of fresh water. The most varied substancescan be used, e.g. fragrances, disinfectants, pH-indicators, etc.

Said substance or substances are protected by a covering, which at theionic concentration, e.g. the pH-value and optionally the temperature ofthe first water filling of the water tank are stable and do not or donot significantly dissolve or become detached. Only when there is asignificant drop in the ionic concentration or the pH-value through anat least partial emptying of the water tank and the inflow of freshwater, i.e. by dilution, is the solubility of the covering materialreduced to such an extent that it rapidly dissolves or becomes detachedand the actual active core material is released into the surroundingmedium.

Provided that charging does not take place by special charging or dosingaids, which can hold back the particles according to the invention, theparticles according to the invention should be sufficiently large toensure that during the emptying of the water tank they are notdischarged to a significant extent.

It is important for the solution according to the invention that thesurface of the particle at most is in partial direct contact with thesurface of the basic composition of the tablet surrounding it. This cantake place in ways specifically described and represented in theapplication, but also in any other way achieving the sought objective.Examples are the loose arrangement of a smaller particle in a largercavity and fixing a smaller particle in a larger cavity in such a waythat there is no or only a partial contact between the particle and thebasic composition of the tablet, etc. Compared with the prior art thisconstellation offers the advantage that during the production process,e.g. the moulding of the individual constituents taking place insuccessive steps, a deformation and possibly resulting damage to thecore or cores and/or the covering is reliably avoided, because thiscould give rise to a reduction of the protective action of the corecovering. If it is ensured that no pressure is exerted on the particleduring any phase of the production process, it is possible to reliablyprevent that in the case of specific core compositions there can be a“bleeding” thereof into the material of the covering and the basiccomposition. It can finally be advantageous for specific compositions ofthe covering or the basic composition to avoid an intimate, full-surfacecontact, because otherwise undesired reactions could arise in theboundary layers.

The term “local environment”, as used in connection with the particlesaccording to the invention, indicates the immediate environment of saidparticles. The ionic concentration in said local environment of theparticle is the determinative factor for the stability thereof. With theproducts according to the invention the ionic concentration in thislocal environment is determined at least up to a substantially completedissolving of the tablet by the ions dissolving therefrom. Preferablythe origin of the “specific ion”, at least in a first phase followingthe addition to the water filling of the water tank, is consequently acompound from the basic composition forming the tablet or is produced byit in the surrounding medium. Typically these are OH— ions (with basiccleaning agents) or H⁺ ions (with acid deliming agents), whoseconcentration can in both cases be expressed as the pH-value.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The invention is described in greater detail relative to the followingexamples and the drawings, wherein the drawings show:

FIG. 1 A first embodiment of the composition according to the inventionin cross-section.

FIG. 2 A second embodiment of the composition according to the inventionin cross-section.

FIG. 3 A third embodiment of the composition according to the inventionin cross-section.

FIGS. 4a & b A fourth embodiment of the composition according to theinvention in cross-section and in plan view.

FIG. 5 A fifth embodiment of the composition according to the inventionin cross-section.

DETAILED DESCRIPTION OF THE INVENTION

In the represented embodiment said cavity receives a single particle 6comprising the core 8 and the pH or ionic concentration-sensitivecovering 9, whose external diameter is slightly smaller than theinternal diameter of the tablet cavity. Both in the representedembodiment, where the particle is loosely received in the cavity, andalso in an embodiment where it is fixed by an adhesive applied to thecavity, it is ensured that there is no continuous, full-surface contactbetween the tablet material and the particle covering. This is animportant aspect of the present invention in order on the one hand toprevent that the protective covering around the particle core from beingdamaged during the production process and on the other for minimizingpossible interactions between the tablet material and the said covering,both with the aim of keeping the covering stable up to a clearly definedtime.

For fixing the particle in the cavity it is obviously not only possibleto use a conventional adhesive, but also other compositions and agentsfulfilling the same function, e.g. a mechanical fixing such as e.g.adequate frictional engagement between tablet and particle at at leastcertain points or a plug connection between tablet and particle. Fixingagents between the particle and tablet can also be constituted bycompounds which optionally melt or dissolve at the temperature of thefirst water filling.

Obviously the most varied further geometrical shapes, such as e.g.ellipsoid, cylinder, etc. are possible for the design of the cavity inthe tablet or the particle received therein. The design and size of thetablet cavity and that of the particle received therein need notcorrespond with one another. Thus, e.g. a spherical cavity can receive acylindrical particle. All possible further combination possibilities areconceivable within the scope of the present invention. It is alsopossible to fill the cavity with several smaller particles instead of asingle particle.

FIG. 2 shows a second embodiment of the inventive composition based on atwo-layer tablet 1. In this case the upper half-tablet 3 comprises twoparts, which make available both an adequate cavity 5 for receiving theparticle 6 and an opening to the tablet side 11. Thus, in this case theparticle 6 is not completely surrounded by the basic composition of thetablet 1, so that it is visible from the outside in the interior oftablet 1. Here again the particle can either be loosely received in thecavity 5 (provided that it is ensured by a corresponding choice of thesize of the particle 6 on the one hand and the size of the opening ofthe cavity 5 towards tablet side 11 on the other that the particle orparticles in the cavity cannot pass through the opening) or can be fixedin the interior of the cavity 5 by a corresponding agent, such as e.g.an adhesive.

FIG. 3 gives a third possible embodiment. The basis for this is a tablet1′, which has a uniform structure, i.e. formed by a single layer 2′ witha uniform composition and colour. By means of a suitable device adepression 4′ is formed in said layer 2′. Into said depression 4′ isintroduced the particle 6′ and in this case is fixed in the depression,because the depression is open to the side 11′ of the tablet 1′ to suchan extent that without any fixing it would be possible for the particleto drop out of the depression and fixing takes place by an adhesive 10′or a fixing intermediate layer or mechanically (e.g. by frictionalengagement). This principle can obviously also be transferred tomultilayer tablets.

Here again the most varied geometrical configurations are possible.Thus, the depression can e.g. have a substantially circularcross-section parallel to the side 11′. However, a random number ofother cross-sections is also conceivable, e.g. any random polygon. Theparticle 6′ received in the depression 4′, as in the embodimentaccording to FIG. 3, can assume any random shape (independent of theshape of the depression 4′), such as e.g. an ellipsoid, cylinder,parallelepiped, etc.

Consideration can also be given to the fixing of the particle 6′ in acavity open at both sides, such as e.g. in a cylindrical hole 4′ passingthrough the tablet body 1′ in which is fixed a corresponding,cylindrical particle 6′ (FIGS. 4a and b).

FIG. 5 gives another possible embodiment. This is essentiallyconstructed in the same way as the embodiment according to FIG. 3, i.e.a tablet 1′, which has a uniform construction, i.e. only a single layer2′ and has a uniform composition and colour. In the present case theparticle 6″ has in place of a single core (as in FIG. 3), numerous cores8″, which are all embedded in a covering 9″. In this embodiment it ise.g. also possible to incorporate cores with a different composition anddifferent shape (encapsulated material or solid cores) in one particle6″.

EXAMPLE 1 Production of the Core

a. Core for a Particle for the Controlled Release of a Fragrance

Oxidizing cleaning agents used in the sanitary sector as additives totoilet cisterns, greatly restrict the choice of fragrances usable inthese compositions. The release of the fragrance only at a time when thecleaning agent has substantially been removed through the running out ofthe water filling of the cistern permits a much greater flexibility inthe use and development of fragrances.

Thus, with the composition according to the invention it is possible forthe first time to combine fragrances with the cleaning agent, whichwould not otherwise be compatible. The tablet comprising the oxidizingcleaning agent dissolves on addition to the cistern, which releases theparticle according to the invention located on or in the tablet andwhose covering prevents the fragrance from being released and thereforeattacked by the cleaning agent. When the cistern is emptied, i.e. thewater filling mixed with the oxidizing cleaning agent flows therefrominto the toilet bowl in order to fulfil its function there, new waterflows in and through the dilution, i.e. the lower pH-value “triggers”the dissolving and detachment of the particle according to the inventionand therefore releases the fragrance-containing core, which can nowevolve its action in the cistern and during the first outflow into thetoilet bowl.

For example, such a fragrance-containing core can be produced in that amolten mixture of 50% melted PEG 8000, 25% fragrance and 25% diethylphthalate is cooled, in order to give e.g. a spherical particle with aweight of e.g. 0.75 g.

b. Core for a Particle for the Controlled Release of a Disinfectant

The optimum bactericidal action of a disinfectant such as benzalkoniumchloride is obtained under neutral or alkaline conditions. Thus, ifbenzalkonium chloride is used in acid cleaning agents (for deliming) itsefficiency is below the optimum.

In the case of the composition according to the invention an acidcleaner tablet for dosing into a toilet cistern can be combined with aparticle according to the invention, whose core contains benzalkoniumchloride as the disinfectant. On adding to the cistern the tabletdissolves and the inventive particle is released, its coveringpreventing the release of the disinfectant in the acid medium inquestion. As soon as the cistern is emptied in order to allow the acidcleaning liquor to drain into the toilet bowl so that it can evolve itsaction, through the inflowing fresh water the dissolving or detachmentof the covering of the particle left behind in the cistern is“triggered”, so that the content can be released from its core and canevolve its optimum action under the given neutral conditions.

A corresponding core for such a particle can e.g. be produced in that amolten mixture of 98% melted benzalkonium chloride and 2% blue dye iscooled in order to form a particle weighing e.g. 0.64 g.

c. Production of a Particle for the Release of a pH-Indicator

If coffee machines are treated with an acid composition (for delimingpurposes), it is not possible to readily establish whether the acid usedhas completely been rinsed out following the treatment. Through the useof an acid tablet with a core containing a pH-indicator, which is onlyreleased in the case of adequate dilution, the implementation of such afunction would become possible.

Such a core particle could e.g. comprise 1 g of a mixture consisting of99.7% sodium chloride and 0.3% of a corresponding indicator (e.g. methylorange or bromocresol green).

EXAMPLE 2 Screening Process for Covering Materials

As stated hereinbefore, it is of great importance for the presentinvention that the material for the covering of the particle core orcores comprises the substance or substances evolving their functionessentially only after an at least partial emptying of the water tankand the inflow of fresh water, only has a solubility which is dependenton the concentration of a specific, selected ion. In this way thecovering is substantially insoluble in that water filling of the watertank, whose ionic concentration is determined by the dissolving of thetablet, and is made soluble and is detached from the particle if theionic concentration drops following an at least partial emptying of thewater tank and the inflow of fresh water.

It has been observed that the dilution, due to the at least partialdraining of the water filling of the water tank with dissolved tabletand the inflow of fresh water, reduces the ionic concentration 10 to 100times, i.e. for example raises or lowers the pH-value by 1 to 2 units.

On the basis of this observation processes have been developed for thescreening of the suitability of different polymers for their use ascovering or enveloping materials, which comprises the determination ofthe solubility of such polymers at two different ionic concentrations,which differ by at least 10 and preferably 100 times.

The ionic concentration values to be used during polymer screening aredependent on the formulation of the basic composition of the tablet intowhich the enveloped or covered particle is to be incorporated.

The value for the highest ionic concentration used for the screeningprocess should correspond to the concentration of the selected ion,which is encountered in the first filling of the water tank, after thebasic composition of the tablet has completely dissolved. When thisconcentration has been determined the lower value for the ionicconcentration should be fixed at 10 to 100 times below this highervalue.

On the basis of this information it falls within the routine capacityand knowledge of an expert in this field to determine the ionicconcentration values of the test solutions to be used in the testingprocesses described hereinafter.

Process for the Preparation of the Test Solution and for Performing andEvaluating the Tests

The materials to be tested are dissolved in solvents in which they arereadily soluble. The solutions are spread over glass plates, then driedat room temperature until they have a constant weight.

At a controlled temperature the glass plates are placed in a beaker withthe test solution. The solution is then stirred with a magnetic stirrerat a controlled stirring rate. After about 10 minutes the glass platesare removed from the beaker and dried at room temperature to a constantweight. The results are expressed as a weight loss (%).

Obviously the screening processes must be adapted to the basiccomposition, because this exercises the essential influence on the ionicconcentration or pH-profile in the water tank. The aim in all cases isto check the degree of solubility of the corresponding materials atdifferent states, namely high or low ionic concentration or pH-value.

On the basis of this information it falls within the routine capacity ofan expert in this field to provide the specific test parameters for thescreening. For example hereinafter two screening processes are describedwith which some of the possible materials for the covering of theparticle according to the invention were tested.

Screening process 1

Screening process 1A was performed with buffer solutions as the mediumfor simulating an alkaline medium. To this end two buffer solutions wereprepared in the following way:

Stock solution: 7.507 glycine buffer (Merck 104169)

 5.850 g NaCl

 topped up with water to 1000 ml

pH 8-buffer solution: 500 ml stock solution

 500 ml distilled H₂O

 1.23 g 1 N NaOH

pH 10-buffer solution: 500 ml stock solution

 500 ml distilled H₂O

 32.6 g 1 N NaOH.

Screening process 1B was performed with buffer solutions as the mediumfor simulating an acid medium. For this purpose use was made of twobuffer solutions commercially available from Merck, namely a citrate/HClbuffer solution with a pH-value of 3 and a citrate/NaOH buffer solutionwith a pH-value of 6.

Screening process 2

Screening processes 2A and 2B were performed with the following basiccomposition formulations, in order to simulate corresponding conditionsin a water tank, e.g. a toilet cistern.

The corresponding compositions were dissolved in water with 17% dH withthe two different concentrations 2 g/l and 0.02 g/l.

Screening process 2A

Alkaline Formulation:

Ingredient wt. % Sodium perborate monohydrate 9.00 Sodiumtripolyphosphate 48.00 Sodium carbonate 28.00 Polyethylene glycol 4.00Polymer 1.50 TAED 3.00 Enzymes 1.50 Surfactant 3.50 Additives 1.50 Total100.00

Screening process 2B

Acid formulation:

Ingredient wt. % Amidosulphuric acid 56 Maleic acid 24 Sodiumbicarbonate 20

Screening process 3

Screening process 3 is used for screening for compounds, whosesolubility changes as a function of the concentration of potassium ions.The compounds found with such a screening process can be used if in thewater tank, as described above, there is a correspondingly highpotassium ion concentration and which is to be correspondingly reducedby the inflow of fresh water.

Screening process 3 was performed with the following formulation inorder to simulate corresponding conditions.

Formulation:

Ingredient wt. % Potassium triphosphate 13.6 Potassium bicarbonate 34.0Potassium sulphate 23.1 Potassium chloride 12.4 Potassium carbonate 9.7Boric acid 2.0 Sodium perborate monohydrate 2.0 TAED 1.0 Paraffin 1.0Protease 0.2

EXAMPLE 3 Choice of Materials for Covering the Particles

Using the screening process described in example 2 different materialswere tested for their suitability as a covering for the particlesaccording to the present invention. One of these materials, hereinaftercalled “Polymer 1” is a polymer as described in Japanese patentapplication KOKAI 61-28440, i.e. a polymer of general formula II with1/(1+m+n)=0.35; m/(1+m+n)=0.45; 1+m+n=1500-1800.

The polymer was produced in conventional manner by bulk polymerization.The screening test results were as follows:

Screening process 1A:

Films of polymer 1 were produced from a 10% solution in isopropanol.

pH-value of buffer solution weight loss at 30° C. [%] 10 7-8 8 81-88

Screening process 2A gave similar good results.

The invention is obviously not restricted to this exemplified polymerand naturally there is a considerable variation possibility with respectto the polymers mentioned in Japanese patent applications KOKAI60-141705, 61-28440, 61-28441, 61-28596, 61-28597 and 61-28598 or can beextended to compounds of formula IV:

in which R₁ independently of one another is hydrogen or an alkyl groupwith 1 to 3 carbon atoms, R₂ independently of one another hydrogen or analkyl group with 1 to 5 carbon atoms and x is an integer from 1 to 6.

Moreover, within the larger class of compounds according to formula III:

in which G is a link group selected from —COO—, —OCO—, —CONH—, —NHCO—,—NHCONH—, —NHCOO—, —OCONH— or —OCOO—, R₁ independently of one another ishydrogen or an alkyl group with 1 to 5 carbon atoms and x is an integerfrom 1 to 6, in exemplified manner it is possible to use polymers with arepeat unit based on a compound of formula VII:

e.g. a pH-sensitive polymer (“Polymer 2”) with the repeat unit VIIIcommercially obtainable under the trademark AEA® from SANKYO:

The above-described screening process 2A was also performed with“Polymer 2”.

15 g of “Polymer 2” and 5 g of Mowiol® 3-98 (Clariant) were dissolved in200 ml of a mixture of water/ethanol/1N HCl 12:8:1. Films were formedand tested in the manner described hereinbefore. The results werecomparable with those of “Polymer 1”.

Further polymers having the desired characteristics or which can besimply modified so as to make them suitable for the purposes of thepresent invention, are polymers of isomers or derivatives of pyridine,preferably copolymers with styrene or acrylonitrile, having thefollowing formulas IX and X, in which G is a substituent at a randompoint of the pyridine ring:

A polymer according to the above formula X, namelypoly(4-vinylpyridine-styrene) copolymer (Scientific Polymer ProductsInc.), namely “Polymer 3” was tested in accordance with theabove-described screening process 2A.

10 g of “Polymer 3” were dissolved in 230 ml of water/1N HCl 6.25:1. Theformation of films and the performance of the tests were as describedhereinbefore. The results were comparable with those for “Polymer 1” and“Polymer 2”.

Further polymers are (e.g. random) polymers derived from chitosan, basedon the following monomer units XI and XII:

In the case where there is a pH-value change from acid to neutral, thefollowing exemplified specific polymers proved suitable in screeningprocesses 1B and 2B:

1. Polyvinyl acetatophthalate

2. Hydroxylpropyl cellulose phthalate

in which R_(1, R) _(2 and R) ₃ are selected independently of one anotherfrom the group comprising methyl, ethyl, carboxymethyl, hydroxyethyl,acetyl,

3. Acrylic acid/ethyl acrylate copolymer

It is possible to use in the covering of the core material substances orsubstance mixtures which, with respect to their solubility behaviour,react to a change in the ionic concentration, i.e. ionicconcentration-sensitive polymers. It is e.g. possible to use the partlyhydrolyzed polyvinyl acetates (commercially available under the tradename Mowiol®-Clariant) described in EP 284 191 A2 and EP 284 334 A2,which have a corresponding ionic concentration dependence in thepresence of borates due to the complexing of the borates with polyols.Initial successful tests were carried out with Mowiol® 56-88.

Another ionic concentration-sensitive polymer is the polysaccharideK-carrageenan, which was proved in screening process 3 (cf. example 2)to be a polymer whose solubility is dependent on the potassium ionconcentration in the surrounding medium. As shown, K-carrageenan has thefollowing formula XI:

This polymer, called “Polymer 4”, was tested in accordance with theabove-described screening process 3.

4 g of K-carrageenan were dissolved in 96 g of water. 10 g of Mowiol®18-88 were dissolved in 90 g of water and both solutions were mixed. Theresulting solution was used for forming films and performing tests, inthe manner described hereinbefore. The following results were obtained:

Cleaning agent concentration Weight loss at 30° C. [%]   4 g/l 0.5-3.00.02 g/l 24.5-25.0

The above list of compounds suitable for the covering according to theinvention is obviously non-exhaustive. Further polymers changing theirsolubility by modifying the pH-value or ionic concentration in thedesired range, are conceivable or can be developed and are consequentlycovered by the protective scope of the present invention. In addition,substances suitable for the covering according to the invention are notlimited to polymeric compounds, although such compounds are describedhere as preferred embodiments.

With the aid of the afore mentioned screening processes or those adaptedto the measurement of an ionic concentration sensitivity, various othercommerically available materials or materials obtainable by simplemodifications, can be investigated for their suitability in the presentinvention. The choice of such polymers is a problem easily solvable bythe average expert in view of the clear aims and the indicated screeningprocesses.

EXAMPLE 4 Production of a Particle According to the Invention

The different cores described in example 1 were used as a basis for theproduction of particles according to the invention. The cores wereprovided individually or in a plurality (FIG. 5) with a covering in anapparatus for applying a film coating of the type known from thepharmaceutical industry (e.g. Lodige, Huttlin, GS, Manesty and Driam).

In cases where the core or cores have an ingredient with a certainincompatibility with the material of the covering, said core or corescan be provided with a protective coating prior to the application ofsaid covering. It is possible to use various prior art materials forthis purpose, such as e.g. cellulose, cellulose derivatives, polyvinylalcohol, polyvinyl alcohol derivatives and mixtures thereof. When usingthe cores of example 1, for 1a use was made of a protective coating andpreferably use was made of a 10 wt. % aqueous solution of a polyvinylalcohol, e.g. Mowiol® 5-88 (Clariant). The applied coating quantity canbe varied and correspondingly adapted by the expert as a function of thecore composition. The cores produced in examples 1b and 1c were directlyprovided with the covering according to the invention without anyadditional protective coating.

The covering can be applied to the core or cores or protective coatingin any random quantity and thickness, provided that it is ensured thatwhen fresh water flows in the covering sufficiently rapidly dissolves orbecomes detached, so that the substance contained in the core or corescan evolve its action. In a preferred embodiment to the cores wereapplied 1 to 10, preferably 4 to 8 wt. % of the ionicconcentration-sensitive covering material (solids), based on the totalparticle weight.

EXAMPLE 5 Production of Tablets According to the Invention

a. Production of a Tablet for use in a Coffee Machine

A two-layer tablet suitable for receiving an inventively coveredparticle in accordance with examples 1c and 4 in a cavity formed in thetablet, can be produced by moulding the pulverulent ingredients inmachines known from the prior art and using operating parameters knownfrom the prior art. One possible shape of such a tablet is aparallelepipedic tablet formed from two substantially identically thicklayers, a hemispherical recess being formed in the large face of each ofthese layers, so that on joining together the two half-tablets asubstantially spherical cavity is formed in the interior (cf. FIG. 1).

The tablet composition can be gathered from the following table 2, bothhalf-tablets being produced with the same composition by compressionunder a pressure of approximately 900 kg/cm

TABLE 2 Ingredient wt. % Amidosulphuric acid 56 Maleic acid 24 Sodiumbicarbonate 20

The total weight of the two half-tablets together is e.g. 20 g. Thecavity resulting from the joining together of the half-tablets shouldhave an internal diameter larger than the external diameter of theparticle according to the invention.

The particle produced according to examples 1c and 4 was introduced intothe hemispherical recess of one of the two half-tablets. This wasfollowed by the application of a fixing substance, e.g. an adhesive(e.g. polyethylene glycol, polyvinyl ether, polyvinyl alcohol, silicate,preferably melted PEG 4000) to the corresponding face of the half-tabletand then the second half-tablet is pressed onto the first.

b. Producing a Tablet for use in a Toilet Cistern

A two-layer tablet suitable for receiving an inventively coveredparticle according to examples 1a and 4 in a cavity formed in thetablet, can be produced by moulding the pulverulent ingredientssubstantially in accordance with examples 5a.

The composition of the tablet can be gathered from the following table3, both half-tablets being produced with the same composition bycompression under a pressure of approximately 800 kg/cm².

TABLE 3 Ingredient wt. % Sodium tripolyphosphate 20.0 Sodium carbonate10.0 Sodium bicarbonate 20.0 Trisodium NTA 8.0 Sodium metasilicate 20.0Sodium sulphate 8.0 Sodium dichloroisocyanurate 8.0 Polymer 1.5 Nonionicsurfactant 4.5

The total weight of the two half-tablets together is e.g. 23 g.

c. Producing a Tablet for use in a Toilet Cistern

A two-layer tablet suitable for receiving an inventively coveredparticle according to examples 1a and 4 in a cavity formed in thetablet, can be produced by moulding the pulverulent ingredientssubstantially in accordance with example 5a. The tablet composition canbe gathered from the following table 4.

TABLE 4 Ingredient wt. % Potassium triphosphate 13.6 Potassiumbicarbonate 34.0 Potassium sulphate 23.1 Potassium chloride 12.4Potassium carbonate 9.7 Boric acid 2.0 Sodium perborate monohydrate 2.0TAED 1.0 Paraffin 1.0 Protease 0.2

d. Producing a Tablet for use in a Toilet Cistern

A two-layer tablet suitable for receiving an inventively coveredparticle according to examples 1b and 4 in a cavity formed in thetablet, can be produced by moulding the pulverulent ingredientsubstantially in accordance with example 5a.

The tablet composition can be gathered from the following table 5, thetwo half-tablets being produced with the same composition by compressionunder a pressure of approximately 900 kg/cm².

TABLE 5 Ingredient wt. % Amidosulphuric acid 56 Maleic acid 24 Sodiumbicarbonate 20

The total weight of the two half-tablets together is e.g. 20 g.

The features of the invention disclosed in the description, claims anddrawings can be essential to the implementation of the differentembodiments of the invention, either singly or in random combination.

What is claimed is:
 1. Composition for use in a water tank characterizedby a base composition (2; 3; 2′) in the form of a tablet (1; 1′), whichevolves its function essentially following addition to a first fillingof the water tank, and at least one particle (6; 6′; 6″) having at leastone core (8; 8′; 8″) comprising at least one substance evolving itsfunction substantially following an at least partial emptying of thefirst filling from the water tank and inflow of fresh water to the sameand a covering (9; 9′; 9″) substantially surrounding the core or coresand comprising at least one compound, whose solubility increases withdecreasing concentration of a specific ion in the surrounding medium, inwhich the at least one particle (6; 6′; 6″) is so placed in or on thetablet (1; 1′) that the surface of said particle is only partly indirect contact with the surface of the base composition (2; 3; 2′)surrounding the same and the concentration of the specific ion in thelocal environment of the particle is sufficiently high to prevent asignificant dissolving of the covering or a significant detachment ofthe covering from the core or cores.
 2. Composition according to claim1, characterized in that the particle or all the particles (6) arereceived in at least one cavity (4, 5) of the tablet (1) completelysurrounded by the base composition (2, 3) and having a larger volumethan the particle or all the particles (6) received in the particularcavity.
 3. Composition according to claim 2, characterized in that theparticle or particles (6) are loosely arranged in the interior of thecavity (4, 5).
 4. Composition according to claim 2, characterized inthat the cavity (4, 5) is substantially centrally arranged in theinterior of the tablet (1).
 5. Composition according to claim 2,characterized in that the particle or particles (6) are fixed in theinterior of the cavity (4, 5).
 6. Composition according to claim 5,characterized in that the particle or particles (6) are fixed by anadhesive in the interior of the cavity (4, 5).
 7. Composition accordingto claim 2, characterized in that the tablet (1) has a single,substantially spherical cavity (4, 5).
 8. Composition according to claim7, characterized in that the cavity (4, 5) receives a single,substantially spherical particle (6), whose external diameter is smallerthan the internal diameter of the cavity.
 9. Composition according toclaim 1, characterized in that the particle or all the particles (6′;6″) are received in at least one cavity (4′) of the tablet (1′) andwhich is only partly surrounded by the base composition (2′). 10.Composition according to claim 9, characterized in that the cavity has adepression (4′) in one of the surfaces (11′) of the tablet (1′) in whichthe particle or particles (6′; 6″) are at least partly received. 11.Composition according to claim 10, characterized in that the cavity ordepression (4′) is only open so wide to the surface or surfaces (11′)that the particle or particles (6′; 6″) received therein cannot passthrough the opening or openings of the cavity or depression (4′). 12.Composition according to claim 11, characterized in that the particle orparticles (6′; 6″) are loosely arranged in the cavity or depression(4′).
 13. Composition according to claim 10, characterized in that theparticle or particles (6′; 6″) are so received in the cavity ordepression (4′) that they do not project over the surface or surfaces(11′) of the tablet (1′).
 14. Composition according to claim 13,characterized in that the cavity or depression (4′) is parallel to oneof the surfaces (11′), to which it is open or in which it is located,and has a substantially circular cross-sectional face.
 15. Compositionaccording to claim 14, characterized in that the particle or particles(6′; 6″) are fixed in the cavity or depression (4′).
 16. Compositionaccording to claim 15, characterized in that the particle or particles(6′; 6″) are fixed with an adhesive (10′) in the cavity or depression(4′).
 17. Composition according to claim 1, characterized in that thecovering (9; 9′; 9″) comprises at least one compound, which is not or isonly slightly soluble at the concentration of the specific ion prior tothe inflow of fresh water and in which the concentration of the specificion following the inflow of an adequate quantity of fresh water has asolubility such that it is so substantially dissolved or detached fromthe core or cores that there is an at least partial escape of the corematerial into the surrounding medium.
 18. Composition according to claim17, characterized in that the compound comprises K-carrageenan. 19.Composition according to claim 17, characterized in that the solubilityof the compound increases with decreasing OH⁻ ionic concentration andtherefore decreasing pH-value in the surrounding medium.
 20. Compositionaccording to claim 19, characterized in that the compound comprises apolymer.
 21. Composition according to claim 20, characterized in thatthe compound comprises a pH-sensitive polymer comprising at least onerepeat unit, which has at least one basic function which is not part ofthe backbone chain of the polymer.
 22. Composition according to claim21, characterized in that the polymer comprises at least on repeat unitbased on a compound selected from the group consisting of one or morevinyl alcohol derivatives, acrylates, and alkyl acrylates comprisingsaid basic function.
 23. Composition according to claim 21,characterized in that the basic function is an amine.
 24. Compositionaccording to claim 21, characterized in that the polymer is acarbohydrate functionalized with said basic function.
 25. Compositionaccording to claim 24, characterized in that the polymer is derived fromchitosan.
 26. Composition according to claim 21, characterized in thatthe basic function is an amine.
 27. Composition according to claim 26,characterized in that the basic function is a secondary or tertiaryamine.
 28. Composition according to claim 27, characterized in that therepeat unit is based on a compound with the following formula III:

in which G is a link group selected from the group consisting of —COO—,—OCO—, —CONH—, —NHCO—, —NHCONH—, —NHCOO—, —OCONH—, and —OCOO, each R₁independently of one another is hydrogen or an alkyl group with 1 to 3carbon atoms, each R₂ independently of one another is hydrogen or analkyl group with 1 to 5 carbon atoms, and x is an integer from 1 to 6.29. Composition according to claim 28, characterized in that the repeatunit is based on a compound with the following formula IV:


30. Composition according to claim 21, characterized in that the basicfunction is a basic aromatic N-containing group.
 31. Compositionaccording to claim 30, characterized in that the basic function is apyridine group.
 32. Composition according to claim 30, characterized inthat the basic function is an imidazole group.
 33. Composition accordingto claim 17, characterized in that the solubility of the compoundincreases with decreasing H⁺ ionic concentration and thereforeincreasing pH-value in the surrounding medium.
 34. Composition accordingto claim 33, characterized in that the compound comprises a polymer. 35.Composition according to claim 34, characterized in that the compoundcomprises a pH-sensitive polymer comprising at least one repeat unit,which is based on a compound comprising an acid function. 36.Composition according to claim 35, characterized in that the polymercomprises at least one repeat unit, which is based on a compoundselected from the group consisting of one or more vinyl alcoholderivatives, acrylates, and alkyl acrylates comprising said acidfunction.
 37. Composition according to claim 35, characterized in thatthe polymer is a carbohydrate functionalized with said acid function.38. Composition according to claim 37, characterized in that the polymeris derived from a polysaccharide by partial esterification of some ofits free hydroxyl groups with a polycarboxylic acid and/or by partialetherification of some of its free hydroxyl groups with a productobtained through the esterification of 1 mole of a polycarboxylic acidwith 1 mole of a polyol.
 39. Composition according to claim 35,characterized in that the acid function is a carboxyl group. 40.Composition according to claim 39, characterized in that the repeat unitis based on a compound with the following formula V:

in which G is a link group selected from the group consisting of —COO—,—OCO—, —CONH—, —NHCO—, —NHCONH—, —NHCOO—, —OCONH—, and —OCOO, each Bindependently of one another is a hydrocarbon group selected from thegroup consisting of straight or branched, saturated or unsaturated, andoptionally substituted alkylenes, arylenes, and aralkylenes, Ak ishydrogen or an alkyl group, each of x, y, and z independently of oneanother is either 0 or 1, and w is an integer from 1 to
 3. 41.Composition according to claim 40, characterized in that the repeat unitis based on a compound with the following formula VI:


42. The composition according to claim 40, characterized in that Ak isan alkyl group with 1 to 4 carbon atoms.
 43. Composition according toclaim 1, characterized in that the core or cores (8; 8′; 8″) comprise atleast one material selected from the group consisting of fragrances,disinfectants and pH-indicators.
 44. Composition according to claim 43,characterized in that the core (8; 8′; 8″) or at least part of the cores(8″) is present in the form of an encapsulated liquid.
 45. Compositionaccording to claim 43, characterized in that the core (8; 8′) or atleast a part of the cores (8″) is present in a solid form.